[kernel] Move pml4 create/delete into vm_space

vm_space and page_table continue to take over duties from
page_manager:

- creation and deletion of address spaces / pml4s
- cross-address-space copies for endpoints
- taking over pml4 ownership from process

Also fixed the bug where the wrong process was being set in the cpu
data.

To solve: now the kernel process has its own vm_space which is not
g_kernel_space.

src/include/kernel_memory.h

@@ -58,4 +58,10 @@ namespace memory {
 		return reinterpret_cast<T*>(a|page_offset);
 	}
 
+	/// Get the number of pages needed for a given number of bytes.
+	/// \arg bytes  The number of bytes desired
+	/// \returns    The number of pages needed to contain the desired bytes
+	inline size_t page_count(size_t bytes) {
+		return ((bytes - 1) & (frame_size - 1)) + 1;
+	}
 } // namespace memory